rcu: Remove CONFIG_PREEMPT_RCU

Now that CONFIG_TREE_PREEMPT_RCU is in place, there is no further need for CONFIG_PREEMPT_RCU. Remove it, along with whatever subtle bugs it may (or may not) contain. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <125097461396-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
git-mirror · Aug 23, 2009 · 6b3ef48 · 6b3ef48
1 parent f41d911
commit 6b3ef48
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Showing 12 changed files with 13 additions and 2,142 deletions.
diff --git a/Documentation/RCU/rcu.txt b/Documentation/RCU/rcu.txt
@@ -36,7 +36,7 @@ o	How can the updater tell when a grace period has completed
 	executed in user mode, or executed in the idle loop, we can
 	safely free up that item.
 
-	Preemptible variants of RCU (CONFIG_PREEMPT_RCU) get the
+	Preemptible variants of RCU (CONFIG_TREE_PREEMPT_RCU) get the
 	same effect, but require that the readers manipulate CPU-local
 	counters.  These counters allow limited types of blocking
 	within RCU read-side critical sections.  SRCU also uses
@@ -79,10 +79,10 @@ o	I hear that RCU is patented?  What is with that?
 o	I hear that RCU needs work in order to support realtime kernels?
 
 	This work is largely completed.  Realtime-friendly RCU can be
-	enabled via the CONFIG_PREEMPT_RCU kernel configuration parameter.
-	However, work is in progress for enabling priority boosting of
-	preempted RCU read-side critical sections.  This is needed if you
-	have CPU-bound realtime threads.
+	enabled via the CONFIG_TREE_PREEMPT_RCU kernel configuration
+	parameter.  However, work is in progress for enabling priority
+	boosting of preempted RCU read-side critical sections.	This is
+	needed if you have CPU-bound realtime threads.
 
 o	Where can I find more information on RCU?
 

diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
@@ -136,10 +136,10 @@ rcu_read_lock()
 	Used by a reader to inform the reclaimer that the reader is
 	entering an RCU read-side critical section.  It is illegal
 	to block while in an RCU read-side critical section, though
-	kernels built with CONFIG_PREEMPT_RCU can preempt RCU read-side
-	critical sections.  Any RCU-protected data structure accessed
-	during an RCU read-side critical section is guaranteed to remain
-	unreclaimed for the full duration of that critical section.
+	kernels built with CONFIG_TREE_PREEMPT_RCU can preempt RCU
+	read-side critical sections.  Any RCU-protected data structure
+	accessed during an RCU read-side critical section is guaranteed to
+	remain unreclaimed for the full duration of that critical section.
 	Reference counts may be used in conjunction with RCU to maintain
 	longer-term references to data structures.
 

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
@@ -94,11 +94,7 @@ extern struct group_info init_groups;
 # define CAP_INIT_BSET  CAP_INIT_EFF_SET
 #endif
 
-#ifdef CONFIG_PREEMPT_RCU
-#define INIT_TASK_RCU_PREEMPT(tsk)					\
-	.rcu_read_lock_nesting = 0,					\
-	.rcu_flipctr_idx = 0,
-#elif defined(CONFIG_TREE_PREEMPT_RCU)
+#ifdef CONFIG_TREE_PREEMPT_RCU
 #define INIT_TASK_RCU_PREEMPT(tsk)					\
 	.rcu_read_lock_nesting = 0,					\
 	.rcu_read_unlock_special = 0,					\

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
@@ -68,11 +68,9 @@ extern int rcu_scheduler_active;
 
 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
 #include <linux/rcutree.h>
-#elif defined(CONFIG_PREEMPT_RCU)
-#include <linux/rcupreempt.h>
 #else
 #error "Unknown RCU implementation specified to kernel configuration"
-#endif /* #else #if defined(CONFIG_CLASSIC_RCU) */
+#endif
 
 #define RCU_HEAD_INIT 	{ .next = NULL, .func = NULL }
 #define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT

diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h
diff --git a/include/linux/rcupreempt_trace.h b/include/linux/rcupreempt_trace.h
diff --git a/include/linux/sched.h b/include/linux/sched.h
@@ -1205,11 +1205,6 @@ struct task_struct {
 	unsigned int policy;
 	cpumask_t cpus_allowed;
 
-#ifdef CONFIG_PREEMPT_RCU
-	int rcu_read_lock_nesting;
-	int rcu_flipctr_idx;
-#endif /* #ifdef CONFIG_PREEMPT_RCU */
-
 #ifdef CONFIG_TREE_PREEMPT_RCU
 	int rcu_read_lock_nesting;
 	char rcu_read_unlock_special;
@@ -1744,14 +1739,6 @@ static inline void rcu_copy_process(struct task_struct *p)
 	INIT_LIST_HEAD(&p->rcu_node_entry);
 }
 
-#elif defined(CONFIG_PREEMPT_RCU)
-
-static inline void rcu_copy_process(struct task_struct *p)
-{
-	p->rcu_read_lock_nesting = 0;
-	p->rcu_flipctr_idx = 0;
-}
-
 #else
 
 static inline void rcu_copy_process(struct task_struct *p)

diff --git a/init/Kconfig b/init/Kconfig
@@ -324,17 +324,6 @@ config TREE_RCU
 	  thousands of CPUs.  It also scales down nicely to
 	  smaller systems.
 
-config PREEMPT_RCU
-	bool "Preemptible RCU"
-	depends on PREEMPT
-	help
-	  This option reduces the latency of the kernel by making certain
-	  RCU sections preemptible. Normally RCU code is non-preemptible, if
-	  this option is selected then read-only RCU sections become
-	  preemptible. This helps latency, but may expose bugs due to
-	  now-naive assumptions about each RCU read-side critical section
-	  remaining on a given CPU through its execution.
-
 config TREE_PREEMPT_RCU
 	bool "Preemptable tree-based hierarchical RCU"
 	depends on PREEMPT
@@ -348,7 +337,7 @@ endchoice
 
 config RCU_TRACE
 	bool "Enable tracing for RCU"
-	depends on TREE_RCU || PREEMPT_RCU || TREE_PREEMPT_RCU
+	depends on TREE_RCU || TREE_PREEMPT_RCU
 	help
 	  This option provides tracing in RCU which presents stats
 	  in debugfs for debugging RCU implementation.
@@ -395,13 +384,6 @@ config TREE_RCU_TRACE
 	  TREE_PREEMPT_RCU implementations, permitting Makefile to
 	  trivially select kernel/rcutree_trace.c.
 
-config PREEMPT_RCU_TRACE
-	def_bool RCU_TRACE && PREEMPT_RCU
-	select DEBUG_FS
-	help
-	  This option provides tracing for the PREEMPT_RCU implementation,
-	  permitting Makefile to trivially select kernel/rcupreempt_trace.c.
-
 endmenu # "RCU Subsystem"
 
 config IKCONFIG

diff --git a/kernel/Makefile b/kernel/Makefile
@@ -82,9 +82,7 @@ obj-$(CONFIG_SECCOMP) += seccomp.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
 obj-$(CONFIG_TREE_RCU) += rcutree.o
 obj-$(CONFIG_TREE_PREEMPT_RCU) += rcutree.o
-obj-$(CONFIG_PREEMPT_RCU) += rcupreempt.o
 obj-$(CONFIG_TREE_RCU_TRACE) += rcutree_trace.o
-obj-$(CONFIG_PREEMPT_RCU_TRACE) += rcupreempt_trace.o
 obj-$(CONFIG_RELAY) += relay.o
 obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
 obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o